Device for calibrating the frequency of an oscillator, phase looked loop circuit comprising said calibration device and related frequency calibration method.

摘要

A device for calibrating the frequency of an oscillator is described. The oscillator (2) has a first and a second input and generates an output frequency (L*S*fo) as a response to a first voltage signal (Vref) applied at the first input. The calibration device (3) is adapted to generate an output digital signal (WD) applied at said second input of the oscillator (2) for calibrating its output frequency (L*S*fo) and it comprises at least one counter (Ti). The counter (Ti) has a first input frequency (fR/2<i-1>) proportional to a reference frequency (fR) and a second input frequency (S*fo) proportional to the output frequency (L*S*fo) of the oscillator (2). The counter (Ti) counts the time window number (Fi) given by the ratio of the second (S*fo) to the first frequency (fR/2<i-1>) and the device (3) comprises means (6) adapted to compare said counted time window number (Fi) with a prefixed time window number (Bi). The calibration device (3) is adapted to change the value of the frequency calibration digital signal (WD) if said counted time window number (Fi) is different from said prefixed time window number (Bi) and until it is obtained that said counted time window number (Fi) is equal to said prefixed time window number (Bi). <IMAGE>